Our LPHN3-OLF structure is very similar to several other OLF domain structures recently determined from LPHN3 (the mouse LPHN3 lectin and olfactomedin-like domains (LPHN3-RBL/OLF)) (Jackson et al., 2015), gliomedin (gliomedin-OLF) (Han and Kursula, 2015), myocilin (myocilin-OLF) (Donegan et al., 2014) and noelin (noelin-OLF) (Pronker et al., 2015) (Table S2, related to Figure 2). Consistently, our LPHN3-OLF structure displays a five-bladed β-propeller folding, i.e. twenty β-strands arranged in five four-stranded, highly twisted, anti-parallel β-sheets (blades) (Figure 2A). The blades are organized around a central conical pore ranging from approximately 6 Å at the “entry” face side to approximately 10 Å diameters at the “exit” face side. One specific feature of our LPHN3-OLF is the disordered 395–403 fragment, which was also disordered in the LPHN3-RBL/OLF structure (Jackson et al., 2015). A noticeable difference between LPHN3-OLF and gliomedin-OLF consists in the presence in the central pore of a Na+ atom instead of Ca2+ in the same position, showing that different metal ions can be found at this site in OLF domains (see below).
